2 
BULLETIN 79, HAWAII EXPERIMENT STATION 
are but a few acres in size. Certain varieties have been named by 
nurserymen there, but, as far as can be ascertained, these are not 
based on extensive tests as to bearing, adaptability, or nut quality. 
The investigations of the Hawaii Agricultural Experiment Station 
here reported consisted of a study of methods of evaluating the mac- 
adamia nut from the standpoint of its use as a commercial article in 
a shelled and roasted form rather than as a table nut in the unshelled 
form. Such an approach appears justified for a number of reasons. 
The present trend in the nut trade is strongly in the direction of ex- 
tracted kernels. Even the thinnest shelled macadamias are difficult 
to c^ack with ordinary instruments owing to the smooth surface and 
tough fibrous nature of the shell, while the thick-shelled nuts offer 
serious obstacles to anything short of commercial machinery. Fur- 
ther, the flavor of the macadamia is greatly enhanced by proper 
roasting or oil cooking and salting. The station's investigations show 
that there is marked variation in kernel quality, and elimination of 
the inferior kernel is necessary to produce a uniform product. This 
is best accomplished in a commercial plant. Selection from this 
standpoint emphasizes the qualities of the extracted kernel which 
adapt it to processing as a roasted product rather than large size of 
nut or paper-thin shell, although these are not to be overlooked. 
Using the methods developed by the station, nuts from the chief 
bearing orchards have been evaluated. Samples of nuts from individ- 
ual trees have been tested for several crops. These show the extent 
to which seedling variation, climate, and type affect the nut char- 
acteristics. It is believed that these data, together with the methods 
of evaluation which have been developed, furnish a basis for an ex- 
tensive study of the several thousand bearing seedling trees of the 
Territory, looking toward the selection of varieties for top working 
and further planting material. 
THE ROUGH-SHELL AND SMOOTH-SHELL TYPES OF MACADAMIA 
NUTS 
There are two distinct types of macadamias in Hawaii, the rough- 
shell type (Macadamia ternifolia) and the smooth-shell type (M. 
ternifolia var. integrifolia) . 2 Presumably both types were brought in 
from Australia where the macadamia is indigenous. The present 
investigation shows that they have marked differences in both 
vegetative and nut characteristics (pis. 1, 2, and 3). Table 1 gives a 
comparison of the two. 
2 There is some question as to whether the smooth-shell type should be classed as a separate species or 
as a variety of Macndnmia ternifolia. For the present, and in this bulletin, the arbitrary term "type" is 
used instead of "species" or "variety." 
